Bladder presses heretofore have been used to shape and cure tire curing press bladders. These bladders are used in tire curing presses to contain high temperature curing media, typically steam, within the interior of the tire for shaping and curing tires. The bladders generally are cylindrical and have one or both ends open depending on the type of tire curing press in which they are used. Most if not all bladders employed in tire curing presses are made of rubber material.
Present day bladder presses for the most part employ compression molding techniques to mold the bladders. These presses have used a large main ram to apply large closing forces to insure rubber flow into the entire mold cavity formed by upper and lower mold parts and a mold core. The main ram also has been used to perform the opening and closing function of the press. To accomplish this the ram had to have a large stroke and this necessitated large capacity hydraulic supply systems.
The main ram typically would be located in the base or bottom bolster of the press which was connected by tie members such as side plates to an upper bolster or press head. The lower mold part would be secured to a lower platen mounted atop the main ram and the upper mold part would be secured to an upper platen mounted to the underside of the top bolster. The mold core would be secured to a core plate movably mounted to the top bolster so that the mold core could be lowered to strip the cured bladder from the upper mold part and then permit removal of the cured bladder from the mold core. To facilitate removal of the cured bladder from the extended core, the core has been provided with an internal air passage by which pressurized air could be supplied to an interior surface of the bladder to cause the same to expand and, in some instances, blow off the mold core. The air passage terminated at an external fitting to which the operator could connect an air line.
In some bladder presses the core plate was actuated by a double rack and gear mechanism and in other bladder presses by piston-cylinder assemblies. In presses designed to mold bladders open at both ends, there has been provided a core ring which cooperates with the lower mold part to form the lower bead of the bladder. To permit removal of the bladder from the lower mold part the core ring can be raised by a core ring pistoncylinder assembly typically housed within the main ram.